It is common practice to refrigerate fish, poultry and vegetables with ice for shipment or for storage while awaiting processing. Typically, chipped or flake ice is simply shoveled into cartons or containers on top of or along with the items to be chilled. Loading containers in this manner is labor intensive and requires constant attention to assure even and effective icing. Flake ice or chipped ice is hard, brittle, and inherently has sharp or jagged edges. These sharp edges can damage the food products as the contents of containers shift during shipment or simply under the weight of the goods and ice packed above lower items in the container. Because flake ice is relatively dry, it can be difficult to move from its point of production to point of use other than by cumbersome and expensive belt- or auger-type conveyors, or hand shovelling. Even so, flake ice is subject to clumping and caking after such ice pieces remain in contact with each other for even a relatively short period of time. Clumps of flake ice are even more likely to cause damage to chilled products as they are rubbed or packed together. Also, because flake ice and clumps of the same have irregular surface areas, the cooling effect of even super-cooled ice can be less than effective, or at least significantly diminished.
Prior art devices have been made which produce and deliver a mixture of ice and water in the form of a slurry or "liquid ice." Such devices are shown in U.S. Pat. Nos. 4,249,388 and 4,833,897. These patents disclose devices with complex agitation blades and baffles for pulverizing the ice pieces and maintaining an homogeneous mixture of ice and water. These devices draw ice and water to be pumped from the bottom of an agitation tank and require the agitation blades to drive the ice pieces, against their natural tendency to float, to this bottom portion of the tank.
A different approach for producing an ice slurry or slush is disclosed in U.S. Pat. Nos. 4,401,449 and 4,796,441. These patents disclose devices which freeze ice crystals in solution as water is subjected to increased pressure and/or decreased temperature. These systems rely on the water being maintained at a critical eutectic concentration (salinity) or pressure. Slight variations in these requirements can cause serious malfunctioning of the device.
Despite the availability of these prior art devices which create an ice slurry or slush ice, it has remained common, particularly in the fish industry, to use dry flake or chipped ice for refrigeration of fresh goods.